Today, with new advanced technology many functions, including analog and digital functions, are internalized in an IC chip. For example, a Coder/Decoder Large Scale Integration (CODEC LSI) device integrates an analog input terminal and a digital signal output terminal As a result, it is necessary for an analog test system to internalize analog test functions together with digital test functions to test an analog IC component.
Some previous analog test systems utilize a DC voltage measuring module to level calibrate, but they can only DC level calibrate with a precision power source and they cannot, for example, calibrate sine waves. Even though some previous analog test systems have the ability to perform AC level calibration, it is necessary to utilize both an AC calibrator (i.e., an AC standard voltage generator) and a digital multimeter which can measure AC voltage. However, AC measuring instruments of high accuracy are costly and rather bulky. Also, they are very sensitive to noise and temperature changes, so that they are difficult and expensive to maintain. In addition, the execution time for calibrating the AC level accuracy of an analog test system is quite lengthy.
FIG. 1 is a block diagram of one example of a conventional analog test system 10. A signal generator 12 includes an analog signal generator 13 and a digital signal generator 14, and supplies test signals to a device under test (DUT) 19 in a test station 11. According to this example, a test signal, originally generated digitally at the digital signal generator 14, passes through a D/A converter 15 and a filter 16 in the analog signal generator 13 and is finally supplied in analog form to an analog signal input terminal 17A of the DUT 19. Also, the digital signal generator 14 generates the digital signals "1" and "0", which are supplied to a digital signal input terminal 17B of the DUT 19.
An analog signal output terminal 18A and a digital signal output terminal 18B are connected respectively to an analog signal measuring unit 21 and a digital signal measuring unit 22 in a signal measuring unit 20. The analog signal measuring unit 21 is composed of a waveform digitizer 23 and a digital signal processor 24. The waveform digitizer 23 receives analog signals from the DUT 19, converts them to digital data signals, and finally directs those digital data signals to the digital signal processor 24. This processor provides a suitable digital process, (e.g., Fast Fourier Transform (FFT)) to the digital data signals output by the waveform digitizer 23. Consequently, an analog signal from the DUT 19 is analyzed digitally by the signal measuring unit 20.
The conventional analog test system 10 of FIG. 1 also includes a power source 25 for supplying power to the DUT 19 and a precision power source 26. The precision power source 26 is utilized for a DC level calibration of the power source 25, the analog signal measuring unit 21, and other units in the analog test system 10. However, since AC measuring instruments are expensive and complicated to use, as has been described, the conventional analog test system has disadvantages in AC level calibration.